One type of optical system has been well known where an external fiber is coupled with an optically active device in the module by a focused optical system not a collimated optical system. Patent Literature 1 has disclosed the collimated optical system in an optical module; meanwhile, Patent Literature 2 has disclosed the focused optical system. The latter optical system has made it possible to align a plurality of optical subassemblies independently with an external optical fiber, which may simplify the aligning process of the module.